Tunable Triple-Shape Memory Binary Mixtures with High Transition Temperature and Robust Mechanical Properties

High temperature triggered shape memory polymers are currently attracting considerable attention due to their potential applications in the context of harsh environments. Herein, tunable dual-and triple-shape memory binary mixture polyimides with high transition temperatures that may meet some of these requirements are presented. The binary mixtures are prepared by blending two poly (amic acid)s of rodlike poly(benzoxazole-imide) (PIB) and flexible polyetherimide (PIO), followed by solvent evaporation and thermal imidization. The aggregation structures, thermal mechanical properties, and shape memory behaviors are systematically studied. It is found that dual-shape memory cycles give excellent shape fixity and recovery of up to 98 and 97%. Moreover, binary mixtures with broad glass transition temperatures endow good triple-shape memory effects and the shape memory at each step crucially depends on the content of the PIB due to the enhancement of physical crosslinks. Additionally, their thermally tough and mechanically strong properties would suggest wide potential applications of the mixtures.